[unreadable] Colorectal carcinoma is the third most commonly diagnosed cancer and the second leading cause of death from cancer in the United States. Often it is diagnosed at an advanced stage, after the patient has developed symptoms, explaining its high mortality rate. Since most cancers arise from polyps over a 5 to 15 year period of malignant transformation, screening programs to detect small polyps less than 1 cm in diameter have been advocated. Unfortunately most people do not follow this recommendation. The health relatedness of this project is to dramatically increase the number of people willing to participate in screening programs by using a convenient, nearly risk-free procedure. [unreadable] [unreadable] Virtual colonoscopy (VC) is a new procedure in which computed tomographic (CT) images of the patient's abdomen are taken and a computer visualization system is used to virtually navigate within a constructed 3-D image model of the colon, mimicking the current gold-standard optical colonoscopy (OC). The broad, long-term objective of this project is to develop VC as an accurate, cost-effective, minimalinvasive, least-stressful technique to screen large segments of the population. [unreadable] [unreadable] To further advance this technology, the specific aims of this project renewal are: (1) to investigate low-dose CT techniques for VC towards massive screening of colonic polyps; (2) to extend electronic colon cleansing strategies to extract the colon mucosa layer by mixture-based image segmentation; (3) to investigate integrated feature-extraction techniques for polyp modeling towards computed aided detection (CAD) of colonic polyps; and (4) to extend our current real-time volume-rendering based navigation algorithms to include CAD and interactive virtual biopsy means for analysis of suspected abnormalities. [unreadable] [unreadable] The research design and methodology will include evaluating from low-dose CT images the ability to electronically clean the colon lumen and extract the mucosa layer with less-stressful bowel preparation; the feasibility of bringing the technology to a readily accessible environment by documenting VC speed and quality with CAD and interactive virtual biopsy tools through the entire colon; and the accuracy by comparing virtual and optical colonoscopy polyp detection in the same patient using a pilot study. [unreadable] [unreadable]